The primary aim of this project is to study the short-latency endocrine events associated with social behavior in adult male rhesus monkeys. These events will be studied using an animal-worn device which permits collection of blood samples without interrupting ongoing behavior. Complementary studies employing venipuncture or collection of samples from chronically catheterized, chair-restrained animals are also included. One group of experiments will expand and clarify our previous observation of rapid increases in testosterone following copulation. The first study is designed to improve our understanding of the prevalence and function of this response. Other studies will attempt to describe some behavioral and physiological characteristics of individual displaying this response and to assess the influence of environmental and social factors on the magnitude and duration of the response. Concommitant measures of luteinizing hormone (LH) and prolactin will provide a clearer picture of hormonal events surrounding copulation. A second group of experiments will study the effects of manipulations of dominance status and aggressive behavior on testosterone and LH, as well as several other hormones which may be responsive to the stress associated with aggressive behavior (prolactin, cortisol and growth hormone). A third group of studies will determine the response of the hormonal systems of interest to such moderate non-social stresses as restraint, capture, and venipuncture. These latter responses will be examined repeatedly in the same animals to determine whether habituation or other changes associated with prolonged or repeated exposure to experimental procedures may influence various hormonal responses. A long-term aim of these experiments is the development of hypotheses concerning the influence of observed hormonl changes in subsequent behavioral events. Along with the behavioral-physiological experiments, we propose to improve the animal-worn blood sampling system to enhance the usefulness of this powerful research technique.